A port conflict occurs when a program is using any of the ports adopted by NoMachine services as it can happen for the WebLogic Server Administration Console, the web-based interface for managing a WebLogic Server domain.

This application uses by default port 7001 (http://[host name]:7001/console), which can be the same port used by the NoMachine display service.    

In this case the WebLogic Server Administration Console starts up successfully, but it will not be possible to perform any operation in the GUI. The error shown in console reports  a message similar to:

The address 127.0.0.1 might be incorrect or another process is using port 7001

The NoMachine display service uses a TCP port which number is defined by the value set in the DisplayBase server configuration key + 6000. By default DisplayBase is set to 1001. This means that NoMachine will try to start the display service on port 1001 + 6000 = 7001 firstly. If this port is already in use, NoMachine will look for a free port by incrementing DisplayBase up to the value set in the DisplayLimit server configuration key. This applies to both the display service started to allow connections to the physical desktop (when an X server is available) and to the display service started for each new virtual desktop.

A solution for resolving this port conflict is to modify the DisplayBase key in NoMachine server configuration file and specify a different value than 1001.

The NoMachine server configuration file is:

BaseDirectory/NX/etc/server.cfg on Linux
BaseDirectory/NoMachine/etc/ server.cfg on Windows
BaseDirectory/NoMachine.app/Contents/Frameworks/etc/ server.cfg  on Mac.

Where BaseDirectory is the installation directory of the NoMachine software.

Edit the server.cfg file, uncomment and set a different value for the DisplayBase key, for example:

DisplayBase 2001

In this way NoMachine will try to start the display service on the 2001 + 6000 = 8001 port firstly.

To make this change effective, restart NoMachine from command line (nxserver –restart) or from the NoMachine GUI.
 

Further references:

Default ports used by NoMachine 4
https://www.nomachine.com/AR01L00770

Solving possible port conflicts
https://www.nomachine.com/AR11L00823